Symmetric and asymmetric diaryl sulfide derivatives are compounds useful as intermediates in the production of many pharmaceutical compounds. For example, bis(3,5-dimethoxy-phenyl)disulfide which is a symmetric diaryl sulfide derivative is a compound useful as an intermediate for the synthesis of dibenzo[b,f]thiepine derivatives. Methods of synthesizing dibenzo[b,f]thiepine derivatives from bis(3,5-dimethoxyphenyl)disulfide have already been described in Japanese Patent Application No. 7904/1996 (International Publication WO97/25985) and so forth.
Compounds bearing a dibenzo[b,f]thiepine skeleton are known to include compounds having a broad range of pharmacological activities such as an anti-inflammatory action [Chemical and Pharmaceutical Bulletin 36, 3462 (1988)], an antispasmodic action (Japanese Patent Public Disclosure No. 160288/1975), an antiestrogenic action [Journal of Medicinal Chemistry 26, 1131 (1983)], an antioxidative action (International Patent Application No. 96/10021), a cerebral function improving action (International Patent Application No. 96/25927), and a trachea dilating action (Japanese Patent Application No. 7904/1996, or International Publication WO97/25985). For effective utilization of these pharmacological activities, a method capable of efficient massive supply of compounds having the dibenzo[b,f]thiepine skeleton is desired.